1. Field of the Invention
The present invlention relates to a device for the chemical vapor deposition coating of small parts, and more particularly to such a device permitting the simultaneous treatment of several small parts and which consists of a reactor with a receptor arranged therein; the receptor having a support fram to receive the parts to be coated and being brought to incandescence by an induction coil.
2. Description of the Prior Art
In the coating of work pieces by means of chemical reactions from the gaseous phase, known as chemical vapor depositin, (CVD), devices similar to applicants' are known from the periodical "Metalloberflache" 30 (1976) 10, page 474, FIG. 1, as well as from VDI-Zeitschrift 114 (1972), page 1222, FIG. 3. However, the reproducibility of the coating characteristics with respect to coating thickness, roughness, adhesion, and hardness of the applied coatings is foten insufficient despite comparable reaction conditions.
Experimentation has revealed three disruptive affects to uniform, reproducible coats:
(1) The layers become thinner in the lower or rear part of the reactor;
(2) Turbulence in the gaseous stream containing the coating or precipitation material causes localized differences in concentration and temperature; and
(3) Intermediate products of the vapor deposition which precipitate on the walls of the reactor can influence the course of the reaction by occasionally causing uncontrollable catalytic effects or, when inductive heating is used, may cause flash-overs.
The deficiencies cited under numbers (1) and (2) can be eliminated by either significantly reducing the gas pressure or by shortening the annealing distance. However either one of these solutions results in a significant reduction of the yield. The problem discussed in (3) has had no solution, until the present invlention as disclosed by applicants herein.
A further disadvantage of the known CVD systems occurs in conjunction with the hardening process, which process is frequently required after the coating of the work pieces. A process where the parts are quenched from the incandescent state using a cold gas stream cannot be optimally carried out in known coating systems because the systems' parts retain heat to such an extent that the cooling process cannot ensue quickly enough. It is therefore necessary to add an additional work step outside of the reactor in which the parts are again annealed and then hardened in a traditional manner.